code: def test_directed_subgraph_hash():
      """
      A directed graph with no bi-directional edges should yield different subgraph hashes
      to the same graph taken as undirected, if all hashes don't collide.
      """
      r = 10
      for i in range(r):
          G_directed = nx.gn_graph(10 + r, seed=100 + i)
          G_undirected = nx.to_undirected(G_directed)
  
          directed_subgraph_hashes = (
              nx.weisfeiler_lehman_subgraph_hashes(G_directed)
          )
          undirected_subgraph_hashes = (
              nx.weisfeiler_lehman_subgraph_hashes(G_undirected)
          )
  
          assert directed_subgraph_hashes != undirected_subgraph_hashes
  
imports: import pytest
  import networkx
  from networkx.generators import directed
label_desc: Use image node_id 14 for calling a global function with example usage: test_directed_subgraph_hash() without return types